1. Field of the Invention
The present invention relates to an image recording material which is appropriate as an image receiving sheet for electrophotography, a method for producing an image recording material and an image forming method using the image recording material.
2. Description of the Related Art
Since electrophotography, which is a dry processing, is excellent in printing speed and able to output an image on general-use paper such as plain paper and fine paper, it has found a wide application in copiers and output devices used in personal computers. In general, image receiving sheets for electrophotography used in the above-described electrophotography have at least a toner image receiving layer on a support, and the toner image receiving layer is formed, for example, by a method in which a thermoplastic-resin containing composition is melted and extruded on the support to have a lamination, a method in which a thermoplastic-resin containing coating solution is coated on the support or others.
Thermoplastic resins used in the toner image receiving layer usually include amorphous polymers, the glass transition temperature (Tg) of which is higher than an environmental temperature and in a temperature range lower by several dozen degrees than a toner fixable temperature. These amorphous polymers are excellent in adhesiveness to toner but are also high in adhesive force between toner image receiving layers containing the toner. Thus, there is found a problem that during storage and transportation of image receiving sheets for electrophotography containing the toner image receiving layer which are superimposed, the toner image receiving layers adhere to each other to result in adhesion failure.
On the other hand, crystalline polymers are low in adhesive force even where the glass transition temperature (Tg) is in a temperature range of below-zero to be free from adhesion failure between the toner image receiving layers containing the crystalline polymer. However, there is a problem that they are deficient in adhesiveness to toner, thereby resulting in removal of toner from the toner image receiving layer after the toner is fixed.
In order to solve the problem, there has been proposed an image receiving sheet for electrophotography in which, for example, a toner image receiving layer contains a mixture of a linear amorphous polymer with a linear crystalline polymer, a glass transition temperature (Tg1(° C.)) of the linear amorphous polymer is 40° C. to 120° C. and a melting point (Tm (° C.)) of the linear crystalline polymer is 100° C. to 200° C. (refer to Japanese Patent Application Laid-Open (JP-A) No. 2005-181881).
Further, there has been proposed an image receiving sheet for electrophotography in which a toner image receiving layer contains a mixture of a linear amorphous polymer with a linear crystalline polymer, and a glass transition temperature (Tg1) of the linear amorphous polymer and a melting point (Tm) of the linear crystalline polymer satisfy the relationship of the following formula (Tg1-20° C.)≦Tm≦(Tg1+20° C.) and also the Tg1 is in a range from 40° C. to 120° C. (refer to JP-A No. 2005-181883).
According to these proposals, it is possible to improve the respective problems of amorphous polymers and crystalline polymers, achieve both favorable toner fixing property and excellent adhesion resistance and also form a highly glossy and high-quality image.
However, in these proposals, a solution prepared by dissolving a mixture of a linear amorphous polymer with a linear crystalline polymer in an organic solvent is used as a coating solution for a toner image receiving layer, thereby causing a serious impact to the environment. Further, in the above proposals, a highly glossy image is obtained where a fixing temperature is high, for example, approximately 155° C. However, on a decrease in fixing temperature, there are found defects such as a decreased gloss and variance in gloss level on a border line between an image portion and a non-image portion. Therefore, when the fixing temperature is decreased for the purpose of saving energy, a problem is posed that only an unpleasant image is obtained which is inferior in uniformity.
In order to obtain a highly glossy and high-quality image, it is necessary that an image receiving sheet should be easily peeled off from a heating roller or a fixing belt and, for this reason, no viscosity should develop on peeling during the course of a temperature decrease (viscoelasticity values). However, no consideration has been so far made for these matters.
There has also been proposed a body to be transferred for a color electrophotographic image having a toner receiving layer formed with a crystalline polyester resin in which an aromatic dicarboxylic acid component is contained as an acid-derived component and straight-chain aliphatic diol, bisphenol S, or bisphenol S alkylene oxide additive is contained as an alcohol derived component (refer to JP-A No. 2005-92097).
Further, there has been proposed an image support material in which a thermoplastic resin of a toner receiving layer is made of a polyester resin prepared by melting and mixing a crystalline polyester resin and an amorphous polyester resin and a viscosity of 103 Pa·s is obtained at temperatures from 80° C. to 110° C. (refer to JP-A No. 2005-99123).
However, in these proposals, there is found a problem that the toner receiving layer is not formed by a coating method but is formed by a melt extrusion method, which requires expensive production facilities and an increased quantity of energy to result in an increased production cost, a greater impact on the environment and a poor quality of the gloss.
Under these circumstances, there is not yet been provided an image recording material having excellent low temperature fixing property and excellent adhesion resistance which is excellent in peeling property from a fixing device, capable of forming a highly glossy and high-quality image and preferable as an image receiving sheet for electrophotography in particular, an effective method for producing the image recording material, or a method for forming an image favorable in fixing-device passing performance by using the image recording material.